During the next grant year, we propose to examine three aspects of the surface proteins of Paramecium: A. The kinetics of synthesis will be studied by the following kinds of experiments - 1. The effect of inhibition of protein turnover on the conservation of "old" label. 2. The effect of an inducer of transformation derived from cells (the 500 g fraction) on synthesis. 3. The effect of cell density on synthesis. 4. A study of the factors affecting overall surface protein concentration. B. Cell-to-cell interactions will be studied by: 1. Determining whether the pattern of transformations of surface proteins induced by 5-FU among unstable clones can provide a guide to the capacity of a clone to act as an effective donor or recipient in transformation induced by cell-free medium. 2. Tracing the fate of cell products using isotopically-labeled cultures. 3. Extending preliminary results which indicate that unstable clones are transformed by stable clones through cell contact without 5-FU pretreatment. C. The induction of transformation by a cell fraction will be studied by: 1. Repeating and extending experiments in which transformation is induced by a 500 g paramecium cell fraction. 2. Determining whether the fraction transforms by binding to surface protein, other proteins, nucleic acids, etc.